Waterproof sheet for use in bridge pier repair and waterproof working method using the same

ABSTRACT

When a bridge pier is reinforced or repaired by wrapping a reinforcement around the pier, a waterproof sheet having a sufficient flexibility to attach to and cover the interface between the pier and the reinforcement in a liquid-tight manner is useful. The waterproof sheet is attached to the interface between the pier and the reinforcement to prevent water from penetrating into the interface for thereby preventing the reinforcement from deterioration.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2012-220342 filed in Japan on Oct. 2, 2012,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a waterproof sheet for use in repair works(commonly known as lining works) for seismic and obsolescentcountermeasures or reinforcements of piers of bridges which are overheadstructures that extend over roads (including ordinary roads andhighways), railways (including Shinkansen and monorails), and obstacles(e.g., water channels), the waterproof sheet being attached to theinterface between the bridge pier and the reinforcement to preventpenetration of rain or water into the interface for thereby preventingthe reinforcement from deterioration. It also relates to a waterproofworking method using the waterproof sheet.

BACKGROUND ART

In conjunction with bridges which are overhead structures that extendover roads, railways, obstacles or the like, repair works are undertakenfor the reinforcement of bridge piers against seismic failure andobsolescent deterioration. Such repair works are commonly known aslining works and include RC lining, steel plate lining and fiber liningas the mainstream works. However, since most bridges or overheadstructures are located in the outdoor environment, they are exposed toweathering including rain, snow and mist. In the prior art, less effortshave been made on the countermeasure against penetration of rain water.Insofar as the inventors know, application of sealants is the only oneknown countermeasure. The steel plate lining and fiber lining methodsrequire cumbersome maintenance and management, and the RC lining methodneeds a long working time. The mortar spraying method is proposed as animprovement over these methods and considered attractive. The mortarspraying method, however, includes a plurality of cumbersome steps, forexample, the thickness of sprayed mortar must be controlled viareinforcing steel guides or the like, and the cure is time consuming.Under the circumstances, if deterioration over time can be suppressed bytaking a countermeasure against penetration of rain water, then someadvantages are expected including an extension of the life of bridgesand a reduction of the expense for maintenance and management. In thecurrent practice of applying sealants, the surface to be applied must bedry. In case of bad weather like rain, snow or mist, workers must waituntil the weather becomes fine and specifically until the wet surfacebecomes dry enough to accept the sealant.

CITATION LIST

Patent Document 1: JP 4076673

Patent Document 2: JP 3580887

Patent Document 3: JP 3748525

Patent Document 4: JP 4509624

Patent Document 5: JP 4910200

SUMMARY OF INVENTION

An object of the invention is to provide a waterproof sheet which isattached to the interface between a bridge pier and a reinforcementwrapped therearound to prevent penetration of rain or water into theinterface for thereby preventing the reinforcement from deterioration,and a waterproof working method using the waterproof sheet. Unlikewaterproof works only with sealants, the surface of a structure can beworked simply after wiping off any residual water with fabric waste orthe like without a need for full drying. The working time can bedrastically shortened.

In one aspect, the invention provides a waterproof sheet for use in amethod for reinforcing and repairing a bridge pier by wrapping areinforcement around the pier, the waterproof sheet having a sufficientflexibility to attach to and cover the interface between the pier andthe reinforcement in a liquid-tight manner.

Preferably, the waterproof sheet has one surface to attach to and coverthe interface, the one surface having tackiness.

In one preferred embodiment, the waterproof sheet is a single layerhaving one surface to attach to and cover the interface, the one surfacehaving been made tacky by heat treatment, flame treatment, electron beamtreatment or acid or base treatment. Alternatively, the one surface hasbeen made tacky by applying a primer or adhesive thereto.

In another preferred embodiment, the waterproof sheet comprises asubstrate layer and a tacky layer which lies on one surface of thesubstrate layer and which is to attach to and cover the interface.

The substrate layer may comprise an unvulcanized or vulcanizedelastomer. Preferably the substrate layer may comprise an elastomerselected from among silicone rubber, EPDM rubber, butyl rubber,chloroprene rubber, and natural rubber. Specifically, the substratelayer comprises an elastomer having a hardness of 10 to 90 on Durometertype A scale, a tensile strength of at least 3 MPa, an elongation of 100to 800%, and a tear strength of at least 3 kN/m.

Typically, the tacky layer is based on an organopolysiloxane.Preferably, the tacky layer is formed of a cured product of an additioncure silicone rubber composition, said composition comprising

-   -   (A) 0 to 100 parts by weight of an organopolysiloxane containing        at least two silicon-bonded alkenyl groups per molecule, having        the average compositional formula (1):        R¹ _(a)SiO_((4-a)/2)  (1)        wherein R¹ is each independently a substituted or unsubstituted        monovalent hydrocarbon group of 1 to 10 carbon atoms, and a is a        positive number from 1.5 to 2.8,    -   (B) 0 to 100 parts by weight of a resinous copolymer        predominantly comprising R₃SiO_(1/2) units and SiO₂ units in a        molar ratio (R₃SiO_(1/2)/SiO₂) of 0.5/1 to 1.5/1, wherein R is a        substituted or unsubstituted monovalent hydrocarbon group and        contains an alkenyl group, a total amount of alkenyl being at        least 0.0001 mol/g, with the proviso that the total amount of        components (A) and (B) is 100 parts by weight,    -   (D) an organohydrogenpolysiloxane containing at least two        silicon-bonded hydrogen atoms per molecule, in an amount of 0.5        to 30 parts by weight per 100 parts by weight of components (A)        and (B) combined, and such that the molar ratio of        silicon-bonded hydrogen in component (D) to silicon-bonded        alkenyl in components (A) and (B) may be in a range of 0.2/1 to        1.5/1, and    -   (E) a catalytic amount of an addition reaction catalyst, the        cured product presenting a tacky surface.

The addition cure silicone rubber composition may further comprise (C) asecond resinous copolymer predominantly comprising R′₃SiO_(1/2) unitsand SiO₂ units in a molar ratio (R′₃SiO_(1/2)/SiO₂) of 0.5/1 to 1.5/1,wherein R′ is a substituted or unsubstituted monovalent hydrocarbongroup, R′ does not contain an alkenyl group or contains an alkenyl groupin a total amount of less than 0.0001 mol/g, in an amount of 0 to 400parts by weight per 100 parts by weight of components (A) and (B)combined. When component (C) contains alkenyl, the molar ratio ofsilicon-bonded hydrogen in component (D) to silicon-bonded alkenyl incomponents (A), (B) and (C) is in a range of 0.32/1 to 0.75/1.

Preferably, the tacky layer has an Asker C hardness of up to 60 and abond strength of 0.5 to 10 N/25 mm to glass.

Typically, the substrate layer has a thickness of 0.2 to 5 mm and thetacky layer has a thickness of 0.3 to 3 mm. Also typically, thewaterproof sheet has a thickness of 0.5 to 8 mm.

In connection with the pier lining work of reinforcing and repairing abridge pier by wrapping a reinforcement around the pier, the inventionprovides a method for waterproof working the bride pier, comprising thestep of attaching the waterproof sheet defined above to the interfacebetween the pier and the reinforcement so as to cover the interface in aliquid-tight manner for thereby preventing water penetration through theinterface.

Typically, the waterproof sheet is directly attached to the interfacewithout a primer.

The waterproof working method may further comprise the step of applyinga sealant to the waterproof sheet so as to cover an edge portion of thewaterproof sheet on the pier and/or reinforcement side. The sealant istypically a silicone sealant.

Advantageous Effects of Invention

In the repair work of wrapping a reinforcement around a bridge pier,so-called pier lining work, a waterproof sheet is attached to theinterface between the pier and the reinforcement to prevent penetrationof rain or water into the interface for thereby preventing thereinforcement from deterioration. The waterproof working method usingthe waterproof sheet allows the working time to be drasticallyshortened.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a waterproof sheet of multilayerstructure in one embodiment of the invention.

FIG. 2 schematically illustrates a bridge pier and a reinforcement.

FIG. 3 is a perspective view of the pier and reinforcement of FIG. 2.

FIG. 4 is a partially cut-away view similar to FIG. 3, showing layers ofthe reinforcement.

FIG. 5 schematically illustrates a waterproof sheet attached to theinterface between the bridge pier and the reinforcement in FIG. 2.

FIG. 6 is a cross-sectional view of a lap joint between two waterproofsheets.

DESCRIPTION OF PREFERRED EMBODIMENTS

As used herein, the term “tacky” is interchangeable withpressure-sensitive adhesive. A region extending across the interfacebetween a pier and a reinforcement where the waterproof sheet isattached is sometimes referred to as “adherend region.”

In conjunction with the repair work of wrapping a reinforcement around abridge pier, so-called pier lining work, the invention provides aflexible waterproof sheet which is attached to the interface between thepier and the reinforcement to prevent penetration of rain or water intothe interface. The waterproof sheet may have either a single layer ormultilayer structure. The waterproof sheet is depicted at 3 in FIG. 1 asa multilayer structure including a substrate 1 and a tacky layer 2.Since its main purpose is waterproofing, the sheet is preferably made ofan elastomer. The elastomer used herein may be either unvulcanized orvulcanized. During shelf storage or prior to use, the waterproof sheetis preferably protected with a cover film.

In one embodiment wherein the waterproof sheet is a single layer, it maybe obtained by adding a tacky agent to a substrate material. Onesuitable material is obtained by blending 1 to 50%, preferably 2 to 30%by weight of a resinous copolymer to be described as component (B) laterin a silicone rubber. Alternatively, the surface of a sheet may be madetacky by carrying out suitable surface treatment such as heat treatment,flame treatment, electron beam (EB) treatment, or chemical treatment(treatment with acid or base). The sheet need not be tacky. Even in thecase where the sheet is not tacky, if the adherend region where thesheet is to be attached is pretreated with a primer, adhesive or thelike, then the sheet may be attached to the region.

In the other embodiment wherein the waterproof sheet has a multilayerstructure, the structure is broadly divided into a substrate layer and atacky layer. It is preferred from the aspects of manufacture of a sheetand handling of a sheet during working that the substrate layer be madeof an elastomer. Although the type of elastomer is not particularlylimited, the preferred elastomers include silicone rubber,ethylene-propylene-diene terpolymer (EPDM) rubber, butyl rubber,chloroprene rubber, butadiene rubber, styrene-butadiene copolymer,urethane rubber, natural rubber, composite silicone rubber/EPDM rubber(available as SEP rubber from Shin-Etsu Chemical Co., Ltd.). For heatresistance, weather resistance and freeze resistance, silicone rubber,EPDM rubber, butyl rubber, chloroprene rubber and natural rubber arepreferred. Inter alia, silicone rubber is most preferred in view of theservice environment which ranges from very cold to very hot climate.

In view of handling of the waterproof sheet, the single layer or thesubstrate layer of the multilayer sheet may be vulcanized orunvulcanized as long as it maintains its shape in the workingenvironment on assumption. The unvulcanized state is exemplified by anunvulcanized silicone rubber composition, unvulcanized butyl rubbercomposition or the like.

When the composition is vulcanized and shaped into a sheet, thevulcanizing method is not particularly limited. In view of a drasticshortening of the working time, the composition of the type which isalready vulcanized into a sheet is preferred to the composition of thetype which is cured in situ. The modes of vulcanization include organicperoxide vulcanization, addition vulcanization, sulfur vulcanization, UVvulcanization, and EB vulcanization.

Any well-known vulcanizing agents may be used for curing the elastomer.In the organic peroxide vulcanization mode, suitable vulcanizing agentsinclude acyl organic peroxides such as p-methylbenzoyl peroxide ando-methylbenzoyl peroxide, alkyl organic peroxides such as dicumylperoxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, percarbonateorganic peroxides and peroxy ketal organic peroxides.

In the addition vulcanization mode, a polymer containing at least twoalkenyl groups per molecule is reacted with a compound having at leasttwo functional groups capable of reacting with alkenyl groups permolecule in the presence of a catalyst. Hydrosilylation reaction is atypical example of this mode. The sulfur vulcanization is a well-knownmode commonly used in the vulcanization of synthetic rubber. In the UVvulcanization (or UV cure) mode, a rubber compound containing apolymerization photoinitiator is cured by irradiating UV of wavelength200 to 400 nm for several seconds to several tens of seconds. UVwavelength used is typically 254 nm or 365 nm. Any well-knownphotoinitiators may be used, for example, Irgacure 184 (BASF). EBvulcanization (or EB cure) is by accelerating electrons and directingthe resulting electron beam to a rubber compound so that the rubbercompound may be cured by utilizing the energy of electron beam. Thedegree of vulcanization is adjustable in terms of accelerating voltageand penetration depth. A typical EB vulcanization system is commerciallyavailable from Iwasaki Electric Co., Ltd.

When the single layer or substrate layer is formed by vulcanizing anelastomer, the vulcanized elastomer should preferably have rubberphysical properties including a hardness of 10 to 90 on Durometer type Ascale, a tensile strength of at least 3 MPa, an elongation of 100 to800%, and a tear strength of at least 3 kN/m. Since these rubberphysical properties are correlated to sheet characteristics, if one ormore of hardness, tensile strength, elongation and tear strength areoutside the range, problems arise during or after application of thesheet. Specifically, if hardness is lower and elongation is greater, thesheet is so deformable that the attachment operation upon application isdifficult and even after the sheet is attached, it may be moved aside.On the other hand, if hardness is higher and elongation is lower, thesheet is less compliant during the attachment operation uponapplication, then an accuracy of positioning is required, adverselyaffecting the working efficiency, and the sheet cannot follow therepeated thermal expansion/contraction of the bridge pier with theambient temperature after application. Further, if tensile strength ortear strength is lower, the sheet cannot withstand the stress appliedthereto by irregularities on the adherend region, becoming sensitive todamages like cuts and tears.

The tacky layer is not particularly limited as long as its surface istacky to the hand in touch. For example, an elastomer, typically butylrubber or silicone resin is used in the uncured state so that it may betacky, or the degree of crosslinking is adjusted so as to remain tacky.Tackiness may be exerted by keeping a certain proportion of functionalgroups in the polymer unreacted.

Described below is the other embodiment of the waterproof sheetincluding a substrate layer and a tacky layer. As described above, thesubstrate is constructed by a rubber, preferably a silicone rubberhaving heat resistance, weather resistance and freeze resistance. Thesilicone rubber is not particularly limited, and any silicone rubbersobtained by curing prior art well-known silicone rubber compositions maybe used. It is preferred from the standpoints of elasticity and rubberstrength to use a silicone rubber having a hardness of 10 to 90, morepreferably 20 to 80 on Durometer A scale according to JIS K6249. Evenmore preferably the hardness of silicone rubber is at least 25,especially at least 40 and up to 80, especially up to 75 on Durometer Ascale. A rubber hardness of less than 10 may lead to low strengthwhereas a rubber hardness in excess of 90 may lead to low elasticity.

Although the silicone rubber composition may be of any cure type, theaddition (or hydrosilylation) reaction cure type or organic peroxidecure type is preferred because molding is completed within a short timeby heating. The silicone rubber composition of addition cure type may beany well-known composition, typically comprising an alkenyl-containingorganopolysiloxane containing at least two alkenyl (typically vinyl)groups per molecule, an organohydrogenpolysiloxane having at least two,preferably at least three SiH groups (typically in such an amount as togive a SiH/alkenyl molar ratio of 0.5/1 to 4/1), and a platinum groupmetal-based addition reaction catalyst, such as platinum or a platinumcompound (typically in such an amount as to give 0.5 to 1,000 ppm ofplatinum group metal based on the weight of the alkenyl-containingorganopolysiloxane). The silicone rubber composition of organic peroxidecure type may be any well-known composition, typically comprising anorganopolysiloxane containing at least two alkenyl groups per moleculeand an organic peroxide in an effective amount as curing agent(typically 1 to 10 parts by weight per 100 parts by weight of theorganopolysiloxane).

The silicone rubber compositions mentioned above are commerciallyavailable. For example, silicone rubber compositions of the additioncure type are available as KE-1935A/B, KE-1950-60A/B and KEG-2000-40A/B,and silicone rubber compositions of the organic peroxide cure type areavailable as KE-551-U, KE-571-U, KE-1571-U and KE-951-U, all fromShin-Etsu Chemical Co., Ltd.

The tacky layer is constructed by a silicone resin or gel havingtackiness. Particularly when a layer is constructed by a silicone resincomposition of the addition cure type, the layer may have a certainrubber hardness and strength as well as sufficient tackiness to bond andattach to the substrate and various parts.

In a preferred embodiment, the tacky layer is formed of a cured productof an addition cure silicone rubber composition comprising (A) anorganopolysiloxane containing at least two silicon-bonded alkenyl groupsper molecule and/or (B) a resinous copolymer predominantly comprisingR₃SiO_(1/2) units and SiO₂ units wherein R is a substituted orunsubstituted monovalent hydrocarbon group and contains an alkenylgroup, (D) an organohydrogenpolysiloxane containing at least twosilicon-bonded hydrogen atoms (i.e., SiH groups) per molecule, and (E)an addition reaction catalyst, the cured product presenting a tackysurface. If desired, the addition cure silicone rubber composition mayfurther comprise (C) a second resinous copolymer predominantlycomprising R′₃SiO_(1/2) units and SiO₂ units wherein R′ is a substitutedor unsubstituted monovalent hydrocarbon group, R′ does not contain analkenyl group or contains an alkenyl group in an amount less than thealkenyl content in component (B).

Component (A) is an organopolysiloxane containing on average at leasttwo alkenyl groups per molecule. It has the average compositionalformula (1):R¹ _(a)SiO_((4-a)/2)  (1)wherein R¹ is each independently a substituted or unsubstitutedmonovalent hydrocarbon group of 1 to 10 carbon atoms, preferably 1 to 8carbon atoms, and a is a positive number in the range of 1.5 to 2.8,preferably 1.8 to 2.5, and more preferably 1.95 to 2.05. Examples of thesilicon-bonded, substituted or unsubstituted, monovalent hydrocarbongroup represented by R′ include alkyl groups such as methyl, ethyl,propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl,hexyl, cyclohexyl, octyl, nonyl and decyl; aryl groups such as phenyl,tolyl, xylyl and naphthyl; aralkyl groups such as benzyl, phenylethyland phenylpropyl; alkenyl groups such as vinyl, allyl, propenyl,isopropenyl, butenyl, hexenyl, cyclohexenyl and octenyl, and substitutedforms of the foregoing in which some or all hydrogen atoms aresubstituted by halogen atoms (e.g., fluoro, bromo or chloro), cyanoradicals or the like, such as chloromethyl, chloropropyl, bromoethyl,trifluoropropyl and cyanoethyl. Preferably, methyl accounts for at least90 mol % of the entire R¹ groups.

It is necessary that at least two R¹ groups be alkenyl groups,preferably having 2 to 8 carbon atoms, more preferably 2 to 6 carbonatoms. It is preferred that alkenyl groups account for 0.0001 to 20 mol%, more preferably 0.001 to 10 mol %, and even more preferably 0.01 to 5mol % of the entire organic groups R¹ (i.e., substituted orunsubstituted monovalent hydrocarbon groups). The alkenyl group may bebonded to a silicon atom at the end of the molecular chain or a siliconatom midway the molecular chain or both. The preferredorganopolysiloxane contains at least alkenyl groups bonded to siliconatoms at both ends of the molecular chain.

Since the degree of polymerization (DOP) is not particularly limited,any organopolysiloxanes ranging from liquid to gum-like at normaltemperature may be used. Typically an organopolysiloxane having anaverage DOP of 50 to 20,000, preferably 100 to 10,000, and morepreferably 100 to 2,000 as measured by gel permeation chromatography(GPC) versus polystyrene standards is used. With respect to thestructure, the organopolysiloxane typically has a linear structure basedon a backbone consisting of repeating diorganosiloxane (R¹ ₂SiO_(2/2))units and capped at each end of the molecular chain with atriorganosiloxy (R¹ ₃SiO_(1/2)) group or hydroxydiorganosiloxy ((HO)R¹₂SiO_(1/2)) group, although it is acceptable that a branched or cyclicstructure be partially included.

Component (B) is a resinous copolymer (or copolymer of three-dimensionalnetwork structure) predominantly comprising R₃SiO_(1/2) units and SiO₂units. Herein R is a substituted or unsubstituted monovalent hydrocarbongroup, preferably having 1 to 10 carbon atoms, more preferably 1 to 8carbon atoms. Examples of the substituted or unsubstituted, monovalenthydrocarbon group represented by R include alkyl groups such as methyl,ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl,neopentyl, hexyl, cyclohexyl, octyl, nonyl and decyl; aryl groups suchas phenyl, tolyl, xylyl and naphthyl; aralkyl groups such as benzyl,phenylethyl and phenylpropyl; alkenyl groups such as vinyl, allyl,propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl and octenyl, andsubstituted forms of the foregoing in which some or all hydrogen atomsare substituted by halogen atoms (e.g., fluoro, bromo or chloro), cyanoradicals or the like, such as chloromethyl, chloropropyl, bromoethyl,trifluoropropyl and cyanoethyl.

The resinous copolymer (B) may consist of R₃SiO_(1/2) units and SiO₂units while it may optionally further contain R₂SiO units and/orRSiO_(3/2) units wherein R is as defined above, in a total amount of upto 50%, preferably up to 40% based on the total weight of the copolymer.The molar ratio of R₃SiO_(1/2) units to SiO₂ units (R₃SiO_(1/2)/SiO₂)should be in a range of 0.5/1 to 1.5/1, preferably 0.5/1 to 1.3/1. Ifthe molar ratio (R₃SiO_(1/2)/SiO₂) is less than 0.5 or more than 1.5, nosatisfactory rubber hardness and strength are obtainable. Further, theresinous copolymer (B) should preferably contain at least two alkenylgroups per molecule. The content of alkenyl is typically at least 0.0001mol/g, preferably 0.0001 to 0.003 mol/g, and more preferably 0.0002 to0.002 mol/g. An alkenyl content of less than 0.0001 mol/g may lead tounsatisfactory rubber physical properties whereas an alkenyl content ofmore than 0.003 mol/g may lead to too high a hardness and hence, a dropof bond strength.

The resinous copolymer may be either a liquid having fluidity at normaltemperature (specifically, a viscosity of at least 10 mPa·s, preferablyat least 50 mPa·s at 25° C.) or a solid having no fluidity at normaltemperature. The resinous copolymer may be obtained from hydrolysis of asuitable chlorosilane or alkoxysilane by the procedure well known in theart.

Components (A) and (B) are combined in such amounts that component (A)is 0 to 100 parts, preferably 20 to 100 parts, and more preferably 30 to90 parts by weight, and component (B) is 0 to 100 parts, preferably 0 to80 parts, and more preferably 10 to 70 parts by weight, provided thatthe total amount of components (A) and (B) is 100 parts by weight.

In a further preferred embodiment, the addition cure silicone rubbercomposition may further comprise (C) a second resinous copolymer inaddition to the resinous copolymer (B), if desired. Component (C) is asecond resinous copolymer (or copolymer of three-dimensional networkstructure) predominantly comprising R′₃SiO_(1/2) units and SiO₂ units.Herein R′ is a substituted or unsubstituted monovalent hydrocarbongroup, preferably having 1 to 10 carbon atoms, more preferably 1 to 8carbon atoms. Examples of the monovalent hydrocarbon group representedby R′ include alkyl groups such as methyl, ethyl, propyl, isopropyl,butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl,octyl, nonyl and decyl; aryl groups such as phenyl, tolyl, xylyl andnaphthyl; aralkyl groups such as benzyl, phenylethyl and phenylpropyl;alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl,hexenyl, cyclohexenyl and octenyl, and substituted forms of theforegoing in which some or all hydrogen atoms are substituted by halogenatoms (e.g., fluoro, bromo or chloro), cyano radicals or the like, suchas chloromethyl, chloropropyl, bromoethyl, trifluoropropyl andcyanoethyl.

The second resinous copolymer (C) may consist of R′₃SiO_(1/2) units andSiO₂ units while it may optionally further contain R′₂SiO units and/orR′SiO_(3/2) units wherein R′ is as defined above, in a total amount ofup to 50%, preferably up to 40% based on the total weight of thecopolymer. The molar ratio of R′₃SiO_(1/2) units to SiO₂ units(R′₃SiO_(1/2)/SiO₂) should be in a range of 0.5 to 1.5, preferably 0.5to 1.3. If the molar ratio (R′₃SiO_(1/2)SiO₂) is less than 0.5 or morethan 1.5, a drop of tackiness occurs. Further, in the second resinouscopolymer (C), the content of alkenyl is typically less than 0.0001mol/g (specifically 0 to 0.0001 mol/g), preferably up to 0.00005 mol/g(specifically 0 to 0.00005 mol/g), and more preferably zero(alkenyl-free). An alkenyl content of more than 0.0001 mol/g may lead toa lack of bond strength.

The second resinous copolymer may be either a liquid having fluidity atnormal temperature (25° C.) or a solid having no fluidity at normaltemperature. A resinous copolymer which is solid at normal temperatureis preferred in view of tackiness of the cured product. The secondresinous copolymer may be obtained from hydrolysis of a suitablechlorosilane or alkoxysilane by the procedure well known in the art.

Preferably component (C) is blended in an amount of 0 to 400 parts, morepreferably 0 to 300 parts by weight per 100 parts by weight ofcomponents (A) and (B) combined. An excessive amount of component (C)may lead to a lack of tackiness and a drop of rubber physicalproperties.

The total content of alkenyl in resinous copolymers (B) and (C) ispreferably in a range of 0.00001 to 0.002 mol/g, more preferably 0.00005to 0.001 mol/g when rubber physical properties and tackiness are takeninto account.

Component (D) is an organohydrogenpolysiloxane containing at least two,preferably at least three silicon-bonded hydrogen atoms (i.e., SiHgroups) per molecule. It serves as a curing agent in that SiH groups inits molecule undergo hydrosilylation or addition reaction withsilicon-bonded alkenyl groups in components (A), (B) and (C) to formcrosslinks for thereby curing the composition. Theorganohydrogenpolysiloxane typically has the average compositionalformula (2):R² _(b)H_(c)SiO_((4-b-c)/2)  (2)wherein R² is a substituted or unsubstituted monovalent hydrocarbongroup of 1 to 10 carbon atoms, b is a positive number of 0.7 to 2.1, cis a positive number of 0.001 to 1.0, and the sum of b+c is 0.8 to 3.0,and contains at least 2 (specifically 2 to 200), preferably 3 to 100,and more preferably 3 to 50 silicon-bonded hydrogen atoms per molecule.Suitable monovalent hydrocarbon groups of R² are as exemplified for R¹,although R² is preferably free of aliphatic unsaturation. Preferably, bis 0.8 to 2.0, c is 0.01 to 1.0, and the sum of b+c is 1.0 to 2.5. Themolecular structure of organohydrogenpolysiloxane may be linear, cyclic,branched or three-dimensional network. Preferred is anorganohydrogenpolysiloxane which is liquid at room temperature (25° C.),specifically in which the number of silicon atoms per molecule, that is,degree of polymerization is 2 to about 300, especially 4 to about 150.The silicon-bonded hydrogen atom may be positioned at the end of ormidway the molecular chain or both.

Also, a third resinous copolymer predominantly comprising R″₂HSiO_(1/2)units and SiO₂ units or a resinous copolymer predominantly comprisingR″₂HSiO_(1/2) units, R″₃SiO_(1/2) units and SiO₂ units may be usedinstead of or in addition to the organohydrogenpolysiloxane havingformula (2). Herein, R″ is a substituted or unsubstituted monovalenthydrocarbon group, which is as exemplified for R′ and preferably free ofalkenyl. The third resinous copolymer may consist of R″₂HSiO_(1/2) unitsand SiO₂ units, or R″₂HSiO_(1/2) units, R″₃SiO_(1/2) units and SiO₂units while it may optionally further contain R″HSiO_(2/2) units,R″₂SiO_(2/2) units, HSiO_(3/2) units and R″SiO_(3/2) units wherein R″ isas defined above, in a total amount of up to 50%, preferably up to 40%based on the total weight of the copolymer. The molar ratio ofR″₂HSiO_(1/2) and R″₃SiO_(1/2) units to SiO₂ units,[(R″₂HSiO_(1/2)+R″₃SiO_(1/2))/SiO₂], is preferably from 0.5 to 1.5, morepreferably from 0.5 to 1.3.

Examples of the organohydrogenpolysiloxane (D) include, but are notlimited to,

-   trimethylsiloxy-endcapped methylhydrogenpolysiloxane,-   trimethylsiloxy-endcapped dimethylsiloxane/methylhydrogensiloxane    copolymers,-   dimethylhydrogensiloxy-endcapped dimethylpolysiloxane,-   dimethylhydrogensiloxy-endcapped    dimethylsiloxane/methylhydrogensiloxane copolymers,-   trimethylsiloxy-endcapped methylhydrogensiloxane/diphenylsiloxane    copolymers,-   trimethylsiloxy-endcapped    methylhydrogensiloxane/diphenylsiloxane/dimethylsiloxane copolymers,-   copolymers of (CH₃)₂HSiO_(1/2) units and SiO_(4/2) units, and-   copolymers of (CH₃)₂HSiO_(1/2) units, SiO_(4/2) units, and    (C₆H₅)SiO_(3/2) units. As used herein, the term “endcapped” means    that a siloxane is capped at both ends of the molecular chain with    the referenced radicals, unless otherwise stated.

The organohydrogenpolysiloxane (D) is blended in an amount of 0.5 to 30parts, preferably 0.6 to 20 parts by weight per 100 parts by weight ofcomponents (A) and (B) combined. No satisfactory rubber strength isobtainable whenever the amount is short or excessive. Also theorganohydrogenpolysiloxane (D) is blended in such an amount that themolar ratio of silicon-bonded hydrogen (SiH) in component (D) tosilicon-bonded alkenyl in components (A), (B) and (C) may be in a rangeof 0.2/1 to 1.5/1, preferably 0.25 to 1.2, and more preferably 0.3 to0.9.

Component (E) is an addition reaction catalyst. Suitable catalystsinclude platinum-based catalysts, for example, platinum black, platinicchloride, chloroplatinic acid, reaction products of chloroplatinic acidwith monohydric alcohols, complexes of chloroplatinic acid with olefins,complexes of chloroplatinic acid with vinylsiloxanes, and platinumbisacetoacetate; palladium-based catalysts; and rhodium-based catalysts.The catalyst may be used in a catalytic amount, which is typically 0.5to 1,000 ppm, preferably 1 to 500 ppm of platinum group metal based onthe total weight of components (A), (B) and (C).

The tacky layer has a hardness which is lower than the hardness ofsubstrate rubber, preferably in the range of 1 to 60, more preferably 2to 55, and even more preferably 2 to 40 on Asker C hardness scale. AnAsker C hardness of less than 1 may lead to poor rubber strength whereasa hardness in excess of 60 may lead to a drop of tackiness.

The tacky layer should preferably have a bond strength of 0.5 to 10 N/25mm, more preferably 0.7 to 8 N/25 mm to glass, as measured according tothe 180° peel test of JIS Z0237 by attaching the layer to glass (FL2.0by Nippon Plate Glass Co., Ltd.), and peeling the layer at an angle of180° and a peel speed of 300 mm/min. A bond strength of less than 0.5N/25 mm is undesirable because of the problem that when the tacky layeris attached to the adherend region, attachment failures may occur due tothe low bond strength of the layer to the region. A bond strength inexcess of 10 N/25 mm may interfere with re-working and re-adheringcapabilities.

To the compositions of which the substrate rubber layer and tacky layerare formed, additional components other than the aforementioned may beadded if desired. Suitable additional components include fillers such asfumed silica, precipitated silica, quartz flour, diatomaceous earth, andcalcium carbonate; electroconductive agents such as carbon black,conductive zinc white and metal powder; and heat resistant agents suchas iron oxide and cerium oxide. Also useful are hydrosilylationregulators such as nitrogen-containing compounds, acetylene compounds,phosphorus compounds, nitrile compounds, carboxylates, tin compounds,mercury compounds, and sulfur compounds; internal parting agents such asdimethylsilicone oil; tackifiers; and thixotropic agents.

Typically the rubber substrate has a thickness of 0.2 to 5 mm,preferably 0.5 to 5 mm, and more preferably 0.5 to 3 mm. A thickness ofless than 0.2 mm may be insufficient to bring out sheet elasticity. Athickness in excess of 5 mm may lead to an increased weight to interferewith attachment operation and an increased cost. Typically the tackylayer has a thickness of 0.3 to 3 mm, preferably 0.5 to 2 mm. A tackylayer of less than 0.3 mm may fail to absorb irregularities on thesurface of the adherend region where the layer is to be attached. Atacky layer in excess of 3 mm may cause rubber failure because therubber strength of the mating surface depends on the tacky layer.

The waterproof sheet of two-layer structure preferably has a thicknessof 0.5 to 8 mm. The waterproof sheet which is a single layer may have athickness of 0.2 to 8 mm, preferably 0.5 to 8 mm, and more preferably0.5 to 5 mm.

The waterproof sheet which is a single layer may be prepared by anywell-known method compliant with its material. The waterproof sheethaving a tacky layer may be prepared by first forming a rubbersubstrate. The rubber substrate may be formed as a single layer using asuitable rubber composition, typically a silicone rubber or EPDM rubbercomposition, or as a composite layer with a metal or another resin. Forexample, a sheet may be directly formed by compression molding, castingor injection molding. A sheet may be formed on a metal substrate, resinsubstrate or resin film by insert molding. Alternatively, dipping,coating, calendering or screen printing may be performed to form arubber sheet integrated with another substrate. It is advantageous thatcalendaring can be effectively used.

Next the rubber substrate is overlaid with a tacky layer. In oneprocedure, a rubber substrate-forming composition is cured to form arubber substrate before the tacky layer is formed thereon. In anotherprocedure, a rubber substrate-forming composition is sheeted on asupport film of polyethylene terephthalate (PET) or the like bycalendering, and a tacky layer-forming composition is applied onto therubber substrate-forming composition in the unvulcanized state. In afurther procedure, the tacky layer-forming composition is applied ontothe rubber substrate-forming composition by a suitable technique such asdipping, coating or screen printing, yielding a multilayer sheet. Thisprocedure is advantageous in that coating can be used for shaping. Inany case, the composition is cured preferably by heating at 80 to 250°C. for 10 seconds to 1 hour. This may be followed by post-cure at 120 to250° C. for 1 to about 100 hours for the purposes of removinglow-molecular-weight fractions or the like.

The waterproof sheet can be used in repair or renovation works of bridgepiers, commonly known as pier lining work, for the purpose of preventingrain or water from penetrating between the bridge pier and areinforcement enclosing the pier. This working operation is describedwith reference to FIGS. 2 to 5. FIG. 2 schematically illustrates abridge pier having a concrete surface. FIG. 3 is a perspective view ofthe pier as separated. A bridge 12 of concrete is supported by a pier 10of concrete on a base or ground and the pier 10 is surrounded by areinforcement 20.

As one example of the bridge pier repair work, the steel-plate liningwork is described. As best shown in FIG. 4, the existing pier 10 ofconcrete defines an interior surface, which is repaired by wrapping thereinforcement 20 therearound. Specifically, a sealer layer 21 and ashrinkage-compensating mortar layer 22 are sequentially deposited aroundthe pier 10, and a steel plate 23 is wrapped as the outermost layer.Although the steel plate is often coated with anti-corrosive paint, theanti-corrosive coating is not complete at the interface 30 between theconcrete pier 10 and the reinforcement 20. Then, after the completion ofrepair work, water originating from rain, snow or mist will deposit onand penetrate into the interface, causing rust. As water penetratesthrough the interface, it acts to reduce the bond strength of the sealerinnermost layer and to render the shrinkage-compensating mortar layerbrittle and liable to peel off. These problems can be solved byattaching a waterproof sheet 3 to the adherend region across theinterface 30 as shown in FIG. 5. If the adherend region is pre-treated,then the sheet may be more effectively attached thereto. Thepre-treatment of the adherend region is not always necessary when thewaterproof sheet has tackiness. When the waterproof sheet having a tackylayer is used, the sheet is attached to the adherend region with itstacky layer facing the region.

The waterproof sheet 3 is attached to the adherend region so that thesheet may completely cover the interface 30. A single waterproof sheetmay be used to circumferentially extend along the interface 30. However,it is more likely to use a plurality of waterproof sheets and arrangethem in juxtaposition along the interface 30 whereby the sheets togethercover the entire interface 30. In this case, the adherend region can beexposed between adjoining waterproof sheets. It is thus preferred thatadjoining waterproof sheets 3 be overlapped to define a lap joint 4 asshown in FIG. 6. The lap joint 4 between sheets 3 preferably has a widthof at least 5 mm, more preferably at least 10 mm, and even morepreferably at least 20 mm. If the width of the lap joint 4 is less than5 mm, sheets may sometimes peel from one another during the attachmentoperation, failing to completely cover the interface 30 and leaving therisk of water penetration. If sheets are largely overlapped, that is, ifthe width of the lap joint exceeds 50 mm, more waterproof sheets arenecessary to completely cover the interface, resulting in an increasedcost.

It is noted that a sealant is preferably applied along both the sideedges of the waterproof sheet on the pier and reinforcement sides. Alsopreferably a sealant 40 is applied on the lap joint 4 between waterproofsheets as shown in FIG. 6. Since the sealant used herein is notparticularly limited, any of well-known silicone, polysulfide andpolyurethane-based sealants may be used. Among others, thesilicone-based sealant is preferred for affinity to the waterproof sheetmaterial. These sealants are commercially available. For example, thesilicone sealants are available as Sealant-Master 300, Sealant 70 andSealant 701 from Shin-Etsu Chemical Co., Ltd.

When a waterproof sheet having tackiness is used as the waterproof sheetof the invention, primerless attachment operation is possible. Then worktime is drastically shortened.

In many previous cases, sealants are directly applied to obsolescentpiers, or no special waterproof measures are taken. When the adherendregion is wet because of rain, snow, or water condensation occurring dueto a climatic temperature difference, weather, moist air or the like,workers must wait until the adherend region becomes dry. On use of thewaterproof sheet of the invention which allows for primerless attachmentoperation, it can be attached even to a wet adherend region as long asthe region is wiped with textile waste or the like to an apparently drystate. This promises the outstanding advantage that repair work can bestarted immediately after the weather has cleared.

Since the waterproof sheet exerts a waterproof function by virtue ofbonding force, the inside can be inspected simply by removing a tiesealer portion at the edge of the sheet. Thereafter, the waterproofsheet exerts a waterproof function again by virtue of bonding force.

EXAMPLE

Examples are given below by way of illustration and not by way oflimitation. All parts and % are by weight. DOP is degree ofpolymerization.

Example 1

A silicone rubber composition was prepared by milling 100 parts ofmillable type dimethylsilicone rubber compound KE-951-U (Shin-EtsuChemical Co., Ltd.) with 20 parts of surface-treated dry silica having aBET specific surface area of 160 m²/g (trade name R8200 by NipponAerosil Co., Ltd.) and 2 parts of a silanol-containingdimethylpolysiloxane having an average DOP of 5 as dispersant on atwo-roll mill and holding in an oven at 100° C. for one hour. Thecomposition was worked into a sheet of 1.5 mm thick.

Example 2

A silicone composition was prepared by providing 100 parts of a basecompound composed of vinyl-containing dimethylsilicone (average DOP6,000) and 80% of crystalline silica, and adding thereto 2.4 parts of anorganohydrogenpolysiloxane having on average two siloxane-bondedhydrogen atoms at the end (SiH content 0.0013 mol/g) and 0.1 part ofvinyl-containing polysiloxane (vinyl content 0.0007 mol/g) as reactionregulator. To the silicone composition, 0.1 part of a platinum catalyst(Pt concentration 1%) was added to form a putty composition. The puttycomposition was press molded at room temperature into a sheet of 1.5 mmthick.

Example 3

A commercially available butyl rubber sheet of 1.5 mm thick (trade nameES-D31510 by Kyowa Co., Ltd.) was used.

Example 4

A silicone rubber composition was prepared by adding 10% of siliconeresin powder (vinyl content 0.0007-0.0010 mol/g) to millable typedimethylsilicone rubber compound KE-551-U (Shin-Etsu Chemical Co.,Ltd.). To 100 parts of the silicone rubber composition was added avulcanizing agent, specifically 0.5 part of C-25A and 2.0 parts of C-25B(both from Shin-Etsu Chemical Co., Ltd.). The mixture was milled on atwo-roll mill and calendered on an embossed PET film of 100 μm thick toform a sheet of 1.5 mm thick. This was heated in a heating furnace at125° C. for 10 minutes, yielding a sheet-shaped product.

Example 5

To 100 parts of millable type dimethylsilicone rubber compound KE-675-U(Shin-Etsu Chemical Co., Ltd.) was added a vulcanizing agent,specifically 0.5 part of C-25A and 2.0 parts of C-25B (both fromShin-Etsu Chemical Co., Ltd.). The mixture was milled on a two-roll milland calendered on an embossed PET film of 100 μm thick to form a sheetof 1.5 mm thick, yielding an unvulcanized silicone rubber composition insheet form (substrate layer).

Using a comma coater, a composition containing 100 parts of a siliconeresin (average vinyl content 0.0085 mol/g), 0.1 part of a platinumcatalyst (Pt concentration 1%) and 1.8 parts oforganohydrogenpolysiloxane (average silicon-bonded hydrogen content0.0009 mol/g) was coated onto the substrate layer and heated in aheating furnace at 125° C. for 10 minutes, yielding a sheet-shapedproduct.

These products were examined for various properties and waterproofness,with the results shown in Table 1.

Tackiness

A 180° peel test was carried out according to JIS Z0237. The sheet wascut to a piece of 25 mm wide and 10 cm long. The sheet piece with itstacky layer inside was attached to a glass plate of 4 mm thick (FL2.0 byNippon Sheet Glass Co., Ltd.) which had been degreased with alcohol andair dried. The sheet piece was peeled from the glass plate at roomtemperature, an angle of 180° and a speed of 300 mm/min, during whichbond strength was measured.

Long-Term Attachment Stability

The sheet was cut to a piece of 25 mm wide and 10 cm long. The sheetpiece with its tacky layer inside was attached to a glass plate of 4 mmthick. The assembly was held at room temperature and 50% RH for onemonth. The sheet piece was peeled from the glass plate at roomtemperature, an angle of 180° and a speed of 300 mm/min, during whichbond strength was measured.

Waterproofness

Waterproofness was evaluated by providing waterproof sheet sections of20 cm wide×100 cm long, and attaching them in continuous juxtapositionto the interface between a bridge pier and a reinforcement as shown inFIG. 5. A sealant, Sealant-Master 300, was applied to a distance of 2 cmfrom the sheet edge toward the pier or reinforcement.

After one month or 6 months from the attachment, a sheet sample shuttingoff rain water penetration is rated good (◯) whereas a sheet sampleallowing rain water penetration is rated reject (x).

TABLE 1 Example 1 2 3 4 5 State clay clay sheet single multilayer un-vulcanized un- layer sheet vulcanized vulcanized sheet, vulcanizedvulcanized Rubber hardness — 45   — 35 74 (Durometer type A) Tensilestrength (Mpa) — — 0.08 9 8.5 Elongation (%) — — 1,000 600 270 Tearstrength (kN/m) — — — 20 10 Asker C (tacky layer) — — 35 — 11 Bondstrength, N/25 mm 2.2 3.6 0.6 2.8 3.5 Long-term attachment stability,2.0 3.6 0.5 2.7 3.4 N/25 mm Waterproofness after 1 month ∘ ∘ ∘ ∘ ∘Waterproofness after 6 months ∘ ∘ ∘ ∘ ∘

Japanese Patent Application No. 2012-220342 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

The invention claimed is:
 1. A waterproof sheet for use in a method for reinforcing and repairing a bridge pier by wrapping a reinforcement around the pier, said waterproof sheet having a sufficient flexibility to attach to and cover the interface between the pier and the reinforcement in a liquid-tight manner, said waterproof sheet comprises: a substrate layer; and a tacky layer which lies on one surface of the substrate layer and which is to attach to and cover the interface, wherein said tacky layer is formed of a cured product of an addition cure silicone rubber composition, said composition comprising: (A) 0 to 100 parts by weight of an organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule, having the average compositional formula (1): R¹ _(a)SiO_((4-a)/2)  (1) wherein R¹ is each independently a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, and a is a positive number from 1.5 to 2.8; (B) 0 to 100 parts by weight of a resinous copolymer predominantly comprising R₃SiO_(1/2) units and SiO₂ units in a molar ratio (R₃SiO_(1/2)/SiO₂) of 0.5/1 to 1.5/1, wherein R is a substituted or unsubstituted monovalent hydrocarbon group and contains an alkenyl group a total amount of alkenyl being at least 0.0001 mol/g with the proviso that the total amount of components (A) and (B) is 100 parts by weight; (D) an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule, in an amount of 0.5 to 30 parts by weight per 100 parts by weight of components (A) and (B) combined, and such that the molar ratio of silicon-bonded hydrogen in component (D) to silicon-bonded alkenyl in components (A) and (B) may be in a range of 0.2/1 to 1.5/1; (E) a catalytic amount of an addition reaction catalyst, said cured product presenting a tacky surface; and (C) a resinous copolymer predominantly comprising R′₃SiO_(1/2) units and SiO₂ units in a molar ratio (R′₃SiO_(1/2)/SiO₂) of 0.5/1 to 1.5/1, wherein R′ is a substituted or unsubstituted monovalent hydrocarbon group, R′ does not contain an alkenyl group or contains an alkenyl group in a total amount of less than 0.0001 mol/g, in an amount of 0 to 400 parts by weight per 100 parts by weight of components (A) and (B) combined, wherein when component (C) contains alkenyl, the molar ratio of silicon-bonded hydrogen in component (D) to silicon-bonded alkenyl in components (A), (B) and (C) is in a range of 0.32/1 to 0.75/1.
 2. The waterproof sheet of claim 1 wherein the tacky layer has an Asker C hardness of up to
 60. 3. The waterproof sheet of claim 1 wherein the tacky layer has a bond strength of 0.5 to 10 N/25 mm to glass.
 4. The waterproof sheet of claim 1 wherein the substrate layer has a thickness of 0.2 to 5 mm and the tacky layer has a thickness of 0.3 to 3 mm.
 5. The waterproof sheet of claim 1, having a thickness of 0.5 to 8 mm.
 6. The waterproof sheet of claim 1 wherein the substrate layer comprises an unvulcanized elastomer.
 7. The waterproof sheet of claim 1 wherein the substrate layer comprises a vulcanized elastomer.
 8. The waterproof sheet of claim 6 wherein the substrate layer comprises an elastomer selected from the group consisting of silicone rubber, EPDM rubber, butyl rubber, chloroprene rubber, and natural rubber.
 9. The waterproof sheet of claim 6 wherein the substrate layer comprises an elastomer having a hardness of 10 to 90 on Durometer type A scale, a tensile strength of at least 3 MPa, an elongation of 100 to 800%, and a tear strength of at least 3 kN/m. 